Use of catheters to administer fluids into and drain fluids out of the body has been a standard practice in medical procedures for years. Many such catheters are available and used as part of an extracorporeal circuit during open-heart procedures.
In a typical open-heart procedure, blood is bypassed from the heart and lungs to a heart lung machine which, in combination with an oxygenator, pumps and oxygenates the blood passing through the extracorporeal circuit. When bypassing the heart, blood is siphoned away from the right atrium and/or vena cava using a venous return (suction) catheter, oxygenated and returned to the aorta using an aortic arch (delivery) catheter. The distal end of the venous return catheter is usually placed in the right atrial appendage and into the inferior vena cava, while the proximal end of the catheter is attached to the tube feeding to a venous reservoir. The venous reservoir is placed at a lower level than the operating table to create a differential head pressure. This differential head pressure acts to siphon blood residing from the inferior vena cava, the superior vena cava, and the right atrium via the venous return catheter into the venous return reservoir. In some cases, an active suction is created by maintaining a vacuum in the venous reservoir. This would help to draw more blood using a smaller cannula.
During the open heart procedure, both the venous return catheter and aortic arch catheter are first introduced into the heart, specifically the right atrium and inferior vena cava of the heart, and the aorta, respectively. The catheters are then clamped to inhibit blood flow therethrough. When the patient is ready to be placed on the extracorporeal circuit, the catheters are connected to inlet and outlet ends of the extracorporeal circuit, respectively, while simultaneously releasing the clamps.
Periodically, during the open-heart procedure, the heart needs to be moved or adjusted by the surgeon. As the venous return catheter is already attached to the heart, there is a potential for the catheter to bend and kink, which can restrict blood flow therethrough and possibly create a dangerous and even life threatening situation. Therefore, the venous return catheter is usually structurally reinforced to prevent kinking.
Sometimes it is desired to utilize a two-stage venous return catheter having multiple sets of openings. A first set of openings at the distal end facilitates drawing blood from the inferior vena cava, whereby a second set of proximal openings facilitate drawing venous blood from the superior vena cava or right atrium of the heart. The second set of proximal venting openings are cumbersome in that the catheter needs to be reinforced about these proximal openings to prevent kinking, yet these proximal openings need to be sufficiently large to draw venous blood therethrough at a sufficient flow rate and pressure and thus reduce the area for reinforcement.
One prior art two-stage venous return catheter is disclosed in U.S. Pat. No. 4,639,252 to Kelley et al. This catheter has a continuous layer of reinforcement material surrounding the proximal drainage openings, these drainage openings being punched through the layer of reinforcing material. The distal portion of the catheter is reinforced with a spring, as is the proximal portion of the catheter proximal of the continuous layer of reinforcing material.
In U.S. Pat. No. 5,769,828 to Jonkman there is disclosed a two-stage venous return cannula with an expandable reinforcing member. The catheter is provided with an expandable reinforcing atrial basket that prevents the cannula from kinking or collapsing about the proximal set of openings. The atrial basket is formed by a plurality of spaced beams.
The two-stage venous return catheter of the '252 Kelley patent and the '828 Jonkman patent both have limitations in that when the catheter is accidentally twisted during the surgery about the proximal openings, the diameter of the lumen therein becomes reduced, thereby restricting venous blood flow therethrough. The device of the '252 Kelley patent may kink at the continuous reinforcement if substantially bent. The device of the '828 Jonkman patent can also kink at the expandable reinforcing member if bent, and may even keep the kinked shape when comprised of a metal material.
There is desired an improved reinforced two-stage venous return catheter having structure adequately reinforcing the proximal openings while maintaining its shape when the catheter is twisted during use and manipulation within the heart during surgery.